GIMP is an acronym for GNU Image Manipulation Program. It is a freely distributed program for such tasks as photo retouching, image composition and image authoring.
It has many capabilities. It can be used as a simple paint program, an expert quality photo retouching program, an online batch processing system, a mass production image renderer, an image format converter, etc.
GIMP is expandable and extensible. It is designed to be augmented with plug-ins and extensions to do just about anything. The advanced scripting interface allows everything from the simplest task to the most complex image manipulation procedures to be easily scripted.
Each task requires a different environment and GIMP allows you to customize the view and behavior the way you like it. Starting from the widget theme, allowing you to change colors, widget spacings and icon sizes to custom tool sets in the toolbox. The interface is modulized into so called docks, allowing you to stack them into tabs or keep them open in their own window. Pressing the tab key will toggle them hidden.